1. Field of the Invention
The present invention relates to a technique for processing a substrate by applying processing liquid onto the substrate.
2. Description of the Background Art
In a manufacturing process of a semiconductor substrate (hereinafter, simply referred to as “substrate”), various processings have been conventionally performed on the substrate, on which an insulating film such as an oxide film is formed, with using a substrate processing apparatus. For example, a processing of etching or the like is performed on a surface of the substrate by applying processing liquid onto the substrate while rotating the substrate around the central axis perpendicular to its main surface. Processing liquid splashed from the rotating substrate is received by a cup part (splash guard) surrounding the substrate, thereby preventing the processing liquid from being splashed outside the apparatus. Such a cup part is normally formed of electrical insulation material such as fluorine resin or vinyl chloride resin, from the viewpoint of corrosion resistance against the processing liquid.
Japanese Patent Application Laid-Open No. 11-283914 (Document 1) discloses a method of preventing a cup part from being charged in processing of a substrate by forming the cup part with antistatic plastic material in a substrate processing apparatus. Japanese Patent Application Laid-Open No. 2004-356299 and Japanese Patent Application Laid-Open No. 2006-147672 disclose substrate processing apparatuses where hydrophilic treatment is performed on an inner annular surface of a cup part or an outer annular surface of an inner cup part in a case where a plurality of cup parts are provided concentrically. In the substrate processing apparatuses, suppressed is re-adherence of processing liquid, which is splashed from a substrate, to the substrate by rebounding from the cup part or the like.
In the meantime, a process using pure water as the processing liquid (cleaning process, for example) is performed in the substrate processing apparatus. In this process, frictional charging in a cup part with insulating properties is caused by pure water with high resistivity (specific resistance) which is splashed from a substrate, and then the main body of the substrate is charged by induction due to electric field generated by the cup part. When processing liquid with conductivity is applied onto the substrate in the above state, insulating properties of an insulating film is broken and electric discharge occurs between the processing liquid applied onto the substrate and the main body of the substrate with interposing the insulating film. Though it is thought to form the whole cup part with antistatic plastic material as disclosed in Document 1, such special material is expensive to greatly increase the manufacturing cost of the substrate processing apparatus.